Catalytic conversion of oil



CATALYTIC CONVERSION OF OIL` Filed Dec. 24, 1941 VENTORS Patentedv 24, 1944 UNITED "STATES PATENT OFFICE i 2,361,182 I l cA'rALmc olvnnslorz oF on. Dn Bois Eastman and Richker, l-ort Arthur, Tex., assignors to The-(Iena Company; New York, N. Y.,a corporation-.of Delaware Application December 24. 1941, Serial No. 424,248

4 Claims. (Cl. 196-52) 'I'his invention relates to the catalytic conversion of hydrocarbon oilto gasoline hydrocarbons suitable for ymotor fuel.

yThe invention has to do with a process for therethrough a highly heated gas containing air or oxygen toburn of! the carbon deposit and thereby restore the activity of the catalyst.

In the regeneration of the catalyst by burning i catalytic conversion of oil by contact with a mass 6 jit is important to avoid exposing the catalyst to of active catalyst in solid fragmentary form contemperatures sulciently highto destroy its acned within a reaction zone, involving alternate tivity. Thus, with an alumina-silica gel type of periods of oil conversion-and catalyst regeneracatalyst it is usually desirable to avoid exposing tion in situ, carbon being deposited upon the it to temperatures much above about 1250 F. catalyst during the conversion periods, and being l Combustion of carbon being `olf a highly exremoved therefrom during the regeneration periothermic nature, large amounts of heat are libods by combustion during flow of an oxygenerated and, therefore provision must be made containing gas through the reaction zone. for removing the liberated heat so as to control The invention broadly contemplates correlatthe temperature prevailing within the contact ing-the conditions of operation during the conmass during regeneration. version periods so as to remain onstream during It has been observedthat the combustion of the conversion periods for a substantial period a carbonaceous deposit from a contact. mass may o'f time, obtaining a'relatively high rate of coninvolve any one of three general types. namely, version to gasoline hydrocarbons and forming a a ilash burn, a diiused burn, and a narrow flame carbonaceous deposit upon the catalyst such that front burn, depending upon conditions prevailduring catalyst regeneration,reactivation can be ing during the regeneration and the extent of confined to a relatively thin sectionA of combus the-carbonaceous deposit. In the ash burn a tion which propagates, in a comparatively gradsuperficial layer of carbon is burned off rapidly, ual manner, from one end to the other end oi while the remaining carbon contained within the the contact mass in the direction o flow' of 25. poresof the catalyst is either not removed or regenerating gas therethrough; else incompletely removed with considerable dif- More specifically, the invention. has to do with flculty. Such type of burn usually occurs where the catalytic cracking of a relatively clean gas the rate ol.' flow 0 1' regenerating gas is quite high, oil stock to form gasoline hydrocarbons wherein i. e., about 10,000 volumes of 4gas (measured at the onstream period of conversion is prolonged atmospheric pressure and temperature) per volto substantially more than 1 hour, as, for exam- 'ume 0f catalyst. ple, a period of about-3 to 4 hours and even The diffused type of burn is one in which all 4 higher, Obtaining a relatively high Yield 0f 88.80- of the carbon throughout the entire mass of the line at least in the range about r"5 to 35% by catalyst is burned substantially simultaneously. weight of the feed oil, and depositing -upon the In such case the catalyst ls usually exposed to catalyst at least 3% and preferably about 5 to excessively high temperatures unless special pro- 15% of carbon by weight of the Catalystvision is made for removing the heat of combus- In catalytic cracking-a stream 0f oil in subtion substantially as rapidly as it is liberated. Starltlally VaDOIZed form and heated 150.8' 00n- Moreover, the exit gases contain substantial vversion temperature vin the range about 800 to 40 amounts of free oxygen., This type of burn iS 1190" F- is Passed through a catalyst bed main associated with a small amount of carbon deposit tained at the. conversion temperature so as to per'umt of catalyst 23232itiibe with the am me mi me f buf panled with concomitant breakdown of a portion A 'acbuflticmlnbon 0a the ron is cgnnmlfd to of the feed oilto gas-and coke or -carbonaceousa :e a i vepy sec on w c mayfrange mn material, which latter is deposited upon the cataabout one'half to several inches in thickness an lyst. As a result of this carbonaceous deposit the this thin section 0f name lrQpagateS relatively activity of the catalyst, vas measured bythe perslowly through the Contact mass ,in the direction' centage conversion to gasoline and gas, decreases. 0f now 0f the reactivating gas- Thus the hot It has been customary lto. operate such a process 2011 Within the Contact mass-is at all times conwith an"exceedingly short conversioncycle or lned t0 a relatively Small area- AS 8. 201158 onstrearn time 'andthereafter terminate the now quence, the liberated heat of combustion can be of feed hydrocarbon through the catalyst bed, vretuilly removed from the contact mass as sensifollowing which the bed is reactivated by passing' 05 ble heat of the reactivating gas, particularly where the oxygen content of the reactivatlng gas is restricted to about 2 or 3% of the reactivating gases and the reactivating gas is caused to ow through the contact mass in relatively large volume. The introduction of oxygen is controlled so that there is complete consumption of oxygen as the flame front advances through the contact mass as indicatedvby the substantial absence of oxygen from the exit gases. In order to vpermit this type of burn it is important to have a rela tively large amount of carbon deposited'on the catalyst.

This narrow flame i'ront type of .regeneration has been found to be preferable since it permits more elcient use of the oxygen content of the reactivating gas and eliminates the necessity for employing extraneous heat carrier media for removing the heat of combustion. Moreover, it has been found that variations over a wide range in the pressure prevailing during regeneration do not change the rate of regeneration appreciably.

Reactivation with a` narrow flame front is disclosed in Liedholm Patent 2,225,402, but the patentee fails to disclose the specific conditions under which the cracking operation must be carried out We have also found that by suitable correlation A of conditions of operation prevailing during the ,conversionv period the length oi' the.,conversion period can be prolonged to substantially in excess of 1 hour, obtaining a relatively high rate of conversion to gasoline while forming a carbonaceous deposit upon the contact mass -to the extent above mentioned. 'I'he conditions of operation which have been found suitable are generally similar to those disclosed in our co-pending applications, Serial No. 313,654, led January 13, y1940 (now U. S. 2,319,590) and Serial No. 409,488, filed September 4, 1941. V

Thus, it is contemplated employing a cracking catalyst of high and sustained activity, such as a catalyst giving an average conversion in excess of 15% and preferably in excess of 25% by weight sures of the order of atmospheric up to about 200 f pounds per square inch'rnay be employed.

t. The charge oil is passed through the contact mass at a space velocity inthe range about 1 to 10 and preferably inthe'range about 3-,to 6' (ex-V pressedas the total liquid lvolume of the chargel vper hour at 60' F. divided by the total volume occupied by the catalyst). Moreover conditions of fluid flow through'thecatalyst mass are maintained such that the modiiied Reynolds number as determined by the` following'equation, has a within the range of about 430 F. to 800. F.:

value of Iabout 40 or 50 and in the fange 0f 100 to 1000.

above and preferably where R is the modified Reynolds number;

Dp is the diameter ofthe catalyst particles in feet;

U is the average velocity in feet per second of uid mixture flowing through the catalyst zone, the zone being regarded as empty;

P is the average density in pounds per cubic foot of uid mixture flowing through the empty zone at the temperature and pressure prevailing during the conversion period;

Z 1 is the viscosity of the duid mixture flowing through the empty zone in pounds per foot per second under the operating conditions of temperature and pressure.

It is advantageous to select as the charge to the conversion reaction a hydrocarbon oil feed stock which is of clean character and good color characterized by having a carbon residue of less than 0.2% and a color of less than 200 as measured on the Lovibond 1/2 inch scale. Various types of feed stocksl having these characteristics can be employed such as kerosene, gas oil and other heavy distillates and even topped crudes and residuals which have been treated to bring them within the characteristics mentioned above.

Furthermore, in heating the feed stock to the reaction temperature it is advantageous to raise the oil to the conversion temperature under conditions such that it undergoes no deleterious change in composition prior to contact with the catalyst. Deleterious change in composition is evidenced by excessive carbon deposition upon the` catalyst during conversion of the oil.

When operating under the foregoing conditions, it has been found that the conversion period of the .operating cycle can be substantially prolonged, for example, to about 3 to 4 hours and even as high as 8 to 20 hours; The conversion rate drops oil' only a comparatively small amount as the conversion period is prolonged to within vthe range set forth above. The rate of carbon deposition on the catalyst also decreases such that the 'ratio of gasoline to carbon with an extended conversion period is much greater than with a relatively short period. This is indicated by the following table comparing 'the results obtained when cracking a virgin gas oil having an A. P. I. Bravity of 30, .a color on the V2 inch Lovibond scale of 7 5, a carbon residue of 0.04%, and boiling .are t ...i car n o Owgs per cent per csn't gasoline per cent 9 by night by wenn: to when by weigh: oi leed oi of leed oil oi catalyst 27. 0 0. 35 7l 1.0 23. 5 0. 20.0 80 2. o 2). 4 0. 24 85 3. 4 18. 1 0. 166 1N 4. 6 .17.0 0. 13 1m 5. 4

4 IF. end point `with a Reid vapor pressure oi 9.5 Pounds.

ofhydrocarbons at the I Ind. Eng. Chem., vol. 28 peinture Viscosities o The foregoing data are illustrative of results obtainable in cracking the gas oil in question by' contact with a synthetic silica-alumina-zirconia catalyst of reduced activity by virtue of previous use, the approximate composition of the catalyst being about 75% SiOz, 20% A1203, and 5% ZrOz by weight, and the catalyst being used in the form of cylindrical pellets V8 inch in diameter and in length.

These results are based on operating conditions involving a reaction temperature of about 925 F., a reaction pressure of about 35 pounds gauge, a space velocity of oil vapors through the catalyst of about 3 (volume of .charge as liquid at 60 F. divided by the total volume occupied by the catalyst per hour), and a modified Reynolds number of about '700 and above. v

As the tabulation shows, with a conversion period of two hours, the ratio of gasoline to carbon produced is about 80, whereas with successively longer periods of conversion this ratio is increased to as much as 130 with a conversion period of twelve hours. In other words, the per cent reduction in gasoline yield by extending the conversion period from two to twelve hours is about 28%, whereas the reduction in carbon is about 55%. Furthermore, it will be observed that by operating with a conversion period of about four hours, the carbon deposited upon the catalyst amounts to about 3.4% by weight of the catalyst, and therefore in an amount sufficient to permit regeneration of the catalyst by narrow flame front burning.

With a fully active catalyst the conversion yield of gasoline would be higher than that shown in the above tabulation. Likewise the yield of carbon would be correspondingly higher. However, the rate of carbon deposition on the cata-- lyst in a catalytic cracking operation is aected by the modiiied Reynolds number maintained during the conversion of the oil. Thus by operating so that a. modified Reynolds number of lower value obtains, the rate of carbon deposition will be greater,

For example, when operating with a. reaction temperature of about 920 F., a reaction pressure of about 40 pounds per square inch gauge, a space velocity of 3, with a. modified Reynolds number of about 65, and using a fully active catalyst of the same composition as aboveQthe following approximate yields are obtained for a three-hour conversion period:

Yield of 400 end point gasoline of 9.5 Reid vapor ured at 32 F. and atmospheric pressure which is passed through a unit volume of catalyst bed per minute). The regeneration pressure may vary from atmospheric up to about 10 atmospheres or more absolute.

By adjusting the oxygen content and the volume of the gas the reactivation may be coniined to a relatively thin lsection which propagates from the inlet to the outlet of the reaction zone, substantially all of the heat of reactivation being removed as sensible heat of the regeneration gases. Moreoven'the entire catalyst mass-can be reactivated in a period of time substantially less than the conversion period.

After switching the feed oil vapor to a catalyst chamber containing reactivated catalyst it is customary to purge the catalyst chamber from which the oil vapor stream was switched with oxygen f ree ilue gas to remove hydrocarbons remaining in the catalyst mass. It has been found advantageous, however, to avoid excessive purging after this switching since excessive purging results in a material reduction in the temperature of the spent catalyst mass and also tends to remove hydrocarbon material, the presence of which is regeneration operation.

pressure 30% by volume-basis feed oil Yield of carbon-- 0.63% by volumebasis feed oil Yield of carbonu 7.5% by weight-basis catalyst 'I'he contact mass containing the carbonaceous -For example, the purge gas should not exceed 10 volumes and preferably should not exceed 4 volumes of gas (measured at the temperature and pressure prevailing in the catalyst chamber during conversion) per volume of catalyst. Moreover, by restricting the volume, the purged gas and entrained hydrocarbons may be discharged directly into the fractionating system without disturbing the fractionating operation unduly.

Reference will now be made to the accompanying drawing for the Apurpose of illustrating briefly the method of operation, p

As indicated, feed oil drawn from a source not shown is forced by a pump l to an oil heater 2 wherein the oil is vaporized and heated to a temperature of about 950 F. The hot oil vapors are then 'conducted through a pipe 3 to catalyst chambers 4 and 4. The chambers are mani fractionator 6.

vapor fraction containing' gasoline hydrocarbons deposit can be activated by passing a mixture of flue gas and oxygen therethrough. The gas ad- The reactvating gas is passed through the from about420 to (space velocity deiined as i the number of volumes of reactivatin gas measand normally gaseous hydrocarbons and a higher boiling liquid fraction comprising gas oil which latter is drawn oi through a pipe 'l for such further disposition as may be desired.

The vapor fraction is drawn'oi from the top prising naphtha is drawn oli through a pipe l2. As indicated in the drawing-a portion of the to 2% by volume.v

conversion mixture passing through the pipe 5 to the fractionator 6 may be diverted through a branch pipe I3. The diverted vapor mixture is recycled by means of a blower I3 to the inlet of the chamber 4. One purpose of this recycling .through the reaction chamber is to increase the volume of hydrocarbons flowing therethrough during conversion and thereby provide a means of increasing the modied Reynolds number to which reference has previously been made.

The flow of hydrocarbons through the cham ber 4 is continued for a period of about 4 hours or longer until it becomes desirable to regenerate the catalyst.

When regeneration becomes necessary the ilow of hydrocarbon vapor is switched from the chamber 4 to the chamber 4' containing fresh or regenerated catalyst. This is accomplished by adjusting the valves in the pipe manifolds leading into and away from the chambers 4 and 4'. The vchamber 4 is then oistream during which time the catalyst contained therein undergoes regeneration.

Prior to such regeneration, however, the chamber is purged with oxygen-free iiue gas or other' inert gas contained in a storage tank -I4. The gas in the storage tank is maintained under suillciently high pressure to force the purged gas through the reaction chambers and to bring the oii'stream chamber up to whatever pressure is desired for the regeneration operation.

Thus, the purged gas is conducted through pipe I5, communicating with a pipe IB leading to the pipe manifold at the inlet of the reaction chambers. "I'his purged gas is forced through lthe oifstream reaction chamber 4 to remove hydrocarbons remaining therein. The exit gas containing entrained hydrocarbons is discharged through the bottom manifold into the pipe 5 and from there is discharged into the fractionator 6. As previously stated the amount of purged gas passed through thereaction chamber is advantageously restricted to not in excess of about 4'volumes of gas per volume of catalyst mass. In this way the temperature of the catalyst mass will not drop more than about F. below the conversion reaction temperature.

Thereafter the outlet valves are adjusted so asI to. bring the purged reaction chamber t0 the pressure level desired for regeneration. As soon as this is done the vregenerating gas discharged by a circulating blower I'I is cut into the reaction chamber. Air or oxygen is introduced to the circulating stream in small amount by a pump or compressor I8. The amount of air introduced is advantageously suiiiclent to maintain an oxygen content in the'recirculating gas of about 1 The circulating blower II is advantageously maintained operating at a substantially constant rate so as to cause a continuous ilow of reactivating gas through the oiistream reaction chamber 4. The exit gas is conducted from the bottom manifold through a pipe 23 which leads to a' .the circulating blower I1.

a suitably controlled valve to the atmosphere or disposed of in some other fashion.

The rate of flow, and the oxygen content, of the circulating gas is adjusted so as to maintain a narrow ilame front of combustion within the reactionchamber as has been described previously. Suillcient volume of inert gas is passed through the catalyst mass undergoing regeneration to absorb exothermic heat of regeneration and to remove it therefrom as sensible heat in the gas issuing from the catalyst mass. More vspecifically conditions are maintained such that substantially all of the exothermic heat of regeneration is removed as sensible heat in the gas, while maintaining the temperature of the catalyst mass not in excess of about 1200 F.

Substantially complete regeneration of the catalyst mass is evidenced by an abrupt drop in temperature ofthe eilluent reactivating gas and by the appearance of oxygen in the eiliuent gas. At this point it becomes desirable to purge the regenerated mass so as to remove residual oxygen.

Purging for this purpose is accomplished by closing a valve 26 in the suction of the blower"l vI'I and allowing the catalyst mass to be purged by oxygen-free gasl from the pressure storage tank I4. In other words, circulation of reacti- Yating' gas through the blower I'I is substantially entirely stopped during this purging step so as to avoid lcontamination of the purge gas with any residual oxygen or oxygen-containing gas that may remain in the system.

The eiliuent purge gas containing residual oxygen is discharged throughthe regenerating gas cooler, pipe 20 and pipe 22.

v As indicated in the drawing a branch pipe 24 containing a control valve 25 may be provided which communicates with the pipe 2l and the pressure storage tank I4. During regeneration of the catalyst mass oxygen-free gas produced during regeneration. particularly` where regeneration is being carried out under a pressure substantially above that prevailing during hydrocarbon conversion, may be conducted through the pipe 24 and valve 25 to the tank I4, thereby restoring the supply of high pressure purge gas.

A pressure oi`about atmospheric or substantially above may be maintained in the reaction chambers during hydrocarbon oil conversion. The same or'substantially higher pressures may prevail during reactivation of the catalyst masses. It is advantageous to employ pressures of 100 pounds and above during reactivation, particularly from the standpoint of reducing the volume ofthe recirculating gas; For example, a

pressure of about 25 to 40 pounds 'may prevail during hydrocarbon conversion, while a pressure oi' 100 to 150 pounds or higher may prevail during reactivation.

`While a synthetic alumina-silica-zirconia type' clays, such asthe Super-Filtrols, are satisfactory. Likewise. the scid-treated uns mem-murmured A"natural or artiiicial zeoliteasuch as the artificial The waste heat boiler serves to abstract heat Excess gas drawn oil' through -a branched pipe 221mm which it may be discharged through- 7lzeolite' known as Doucil, can be used. Various metals can be substituted in the clays or zeolites.'

such as uranium, molybdenum.v manganese, lead; zinc. zirconium, nickel and the like. the combination of certain acid-treated active clays of the character ot Filtrol. together with added proportions of alumina or silica or both can bel employed. Alumina alone may be used under certain conditions. The synthetic silica-alumina f catalysts can be improved by the addition f other constituents, such as zirconium oxide or molybdenum oxide. Other catalysts which are 'not silica-alumina catalysts, either synthetic or pre pared from natural minerals, have been found which satisfyfthe characteristics of the catalyst of the present invention. Examples of other suitable catalysts comprise metallic halide compounds suchas the halides of aluminum and chromium, etc. In general, a catalyst is employed which is stable at high temperatures of the order of 1400 to 1600 F., as determined by calcining in a munie furnace at that temperature, and which is a measure or indication of the ability of the catalyst to maintain its activity under the customary temperatures of reactivation of the order of 1100 to 1400" F., as measured by thermocouples within the catalyst bed during the reactivation cycle. It is preferred to employ a catalyst which is substantially free from/ alkali and alkaline earth metals.

Also if desired the conversion reaction may be carried out in the presence of light gases such as hydrogen and hydrogen-containing gases, including gases produced in the reaction and which may be recirculated through the heating and conversion zones or through the conversion zone only.

In the appended claims the term fragmentary used with vreference to the catalyst is ern-V ployed in a generic sense to include all forms in which a solid catalyst may be used, forexample, powder, particles, granules, lumps, pellets and pills, etc.

Obviously many modifications and variations of the inventionvas above set forth may be made Without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated by the appended claims.

We claim:

1. In the catalytic cracking of hydrocarbon oil to convert the same to gasoline hydrocarbons during passage through a bed of active cracking catalyst within a reaction zone involving alternate periods of oil conversion and catalyst regeneration in situ, carbon being deposited upon the catalyst during the conversion periods and being removed therefrom by combustion during the regeneration periods by ow of combustion drocarbons through the catalytic mass, and regenerating said mass in situ while confining reactivation to a relativelythin section which propagates from inlet to outlet of said reaction zone.

2. The method according to claim l in. which the hydrocarbon flow is continued through the catalyst mass during the onstream period for at least 3 hours.

3. In the catalytic cracking of hydrocarbon oil to convert the same to vgasoline hydrocarbons duringpassage through a bed of active cracklng catalyst within a reaction zone involving alternate periods of oil conversion and catalyst regeneration in situ, carbon being deposited upon the catalyst during the conversion periods and being removed therefrom by combustion during the regeneration periods by ow of combustion gases containing about 1 to 2% oxygen at a gas space velocity of about 20 to 100 through the bed from inlet to outlet of the reaction zone, substantially all of the heat of combustion being removed entirely as sensible heat of the eilluent gas Withoutexposing the catalyst'mass to temperatures above about 1250o F., the method which comprises heating a :leed oil consisting essentially of normally liquid hydrocarbons having a carbon residue of less than 0.2% and a color of less than 200 on the Lovibond 1/2" scale to a temperature in the range 950 to 1050 F., passing the heated oil in vapor phase through the catalyst mass at a space velocity in the range 3 to 6, maintaining a rate of hydrocarbon flow through the mass corresponding to a modified Reynolds flow number in the range 100 to 1000, continuing the flow of hydrocarbons through the mass without interruption for regeneration for a period of at least 3 to 4 hours until carbonaceous deposit formed on the catalyst amounts to about 5 to 15% by weight of the catalyst, at least about 17% byl weight of the feed oil being converted into gasoline, thereafter interrupting the flow of hydrocarbons through the catalytic mass, and regenergases containing about 1 to 2% oxygen at a gas space velocity of about 20 to 100 through the bed from inlet to outlet of the reaction zone, substantially all of the heat of combustion being removed entirely as sensible heat of the effluent gas without exposing the catalyst mass to tem.

oil in vapor phase through the catalyst mass at a space velocity in the range 1 to 10, maintaining a rate of hydrocarbon ow through the mass cor-v responding to a modified Reynolds flow numberin the range 100 to 1000, continuing the flow of hydrocarbons through the mass without interruption for regeneration for a periodsubstantially in excess of 1. hour until oarbonaceous deposit formed on the catalyst amounts to about 5 to `,15% by weightof the catalyst, at least about 17% by weight of the feed oil being converted into gasoline thereafter interrupting the iiow of hyating said mass in situ while confining reactivation to a relatively thin section which propagates from inlet to outlet of said reaction zone.

4. In the catalytic cracking of hydrocarbon oil to convert the same to gasoline hydrocarbons during passage through a bed of active cracking catalyst within a reaction zone involving alternate periods of oil conversion and catalyst regeneration in situ, carbon being deposited upon the catalyst during the conversion periods and .being removed therefrom by combustion during the regeneration periods by iiow of combustion gases containing about 1 t@ 2% oxygen at a gas space velocity of about 20 to 100 through the bed from inlet to outlet of the reaction zone, substantially all of the heat of combustion being removed entirelyas sensible heat of the effluent gas without exposing the catalyst mass'to temperatures aboveabout 1250 F., the vmethod which comprises heating a feed oil consisting essentially of normally liquid hydrocarbons having a carbon residue of less than 0.2% and a color of less than 200 on) the Lovibond 1/2 scale to a temperature in the. range 950 to 1050 F., passing the heated oil in vapor phase through the catalyst mass at a space velocity in the range 3 to 6, maintaining a rate of hydrocarbon flow through the mass corresponding to a modiiied- Reynolds flow number in the range to 1000, continuing the flow of hydrocarbons through the catalytic mass without interruption for regeneration for a period substantially in excess of 1 hour until carbonaceous deposit formed upon the catalyst amounts to about -5 to 15% by weight of the cata,- lyst, a substantial portion of the feed oil being converted into gasoline and the ratio of gasoline to carbon being produced when the catalyst has been onstream for substantially more than v1 hour being substantially greater than that obtaining during a period of 1 hour and less, thereafter interrupting `the ilow` of hydrocarbons through the catalyst mass, andy regenerating said mass in situ while confining reactivation to a relatively thin section which propagates from in- 5 let to outlet of said reaction zone.

DUBOIS EASTMAN. CHARLES RICHKER. 

